Manufacture of rayon



Patented Mar. 28, 1944 MANUFACTURE OF RAYON Theodoor Koch, oosterbeek, Netherlands, assignor to American Enka Corporation, Erika, N. 0., a corporation of Delaware No Drawing. Application April 1, 1940, Serial No. 327,291. In Germany August 1, 1939 3 Claims.

This invention relates to the manufacture of rayon, and more particularly to the manufacture of rayon having a wool-like character. The invention is applicable to any type of regenerated cellulose rayon, but for the sake of convenience will be described in its specific application to yarns produced by the viscose process.

In the textile industry it is frequently desirable to mix rayon yarns with natural wool yarns in the production of fabrics, but this practice has been limited, because of the lack'of affinity of rayon yarns for the acid wool dyes employed in the dyeing of natural wool, the result being undesirable differences in coloration of the fabric.

It has been sought to overcome this obstacle by the addition of substances to the viscose spinning solution capable of giving to the rayon a wool-like character and at the same time efiect an ailinity for acid wool dyes. For this purpose it has been proposed to mix proteinous materials such as casein, albumins and the like with the spinning solution to be spun. However, while the rayon yarns produced in this manner have exhibited the desired afiinity for acid wool dyes, they have been so defective from the standpoint of tensile strength that they have been of little practical value. The reason for this low tensile strength may be ascribed to the failure to obtain a homogeneous mixture of proteinous material with the cellulosic solution,-the result being that the spun threads have not been of homogeneous structure.

In order to produce an improved spinning solution comprising a homogeneous mixture of viscose and proteinous material, it has been proposed to effect a high dispersion of the protein in the viscose solution by means of suitable apparatus. However, a degree of dispersion sufficient to impart homogeneity to the spinning solution was found to be of little advantage, since it was very unstable and subsequently separated into its components.

Another object of the invention is the manufacture of an improved rayon yarn spun from a cellulosic solution containing a protein.

A further. object of the invention is a method of manufacturing an improved rayon yarn having a Wool-like character.

It has been determined that a homogeneous spinning solution can be produced from a cellulose-protein mixture, for example a viscosecasein mixture, if the casein is subjected to a measured chemical decomposition prior to its addition to the viscose solution. The decomposition of the casein need only be carried out to such an extent that it will mix readily with the viscose and will coagulate rapidly enough in the acid precipitating bath so that it will be carried forward with the spun yarn and become a part thereof. The extent to which decomposition should be carried out in order to produce a homogeneous mixture of casein and viscose may be easily determined by a microscopic study of a portion of the mixture, which should appear homogeneous throughout, and the addition of a dilute acid should instantly cause substantially complete coagulation.

Other proteins that are suitable for use in conjunction with the present process are soy bean proteins and zein.

It has also been proposed to mix with the The decomposition of the proteinous material may be efiected by hydrolysis with steam under pressure, or by the use of acids, alkalies, or enzymes. For example, if casein is employed as the proteinous material the casein may be subteins, or from cellulosic solutions containing proteins, are attacked by alkaline solutions, the protein content frequently dissolving out and destroying the wool-like character of the thread. In order to prevent the protein from reacting with the alkaline solution, the thread is usually treated with aldehydes, particularly formaldehyde solutions, to harden the protein content and render the threads resistant to the alkaline after-treatment. It has now been found that this hardening treatment of the yarn can be ,areneutralizedi V Byfthe' direct addition'of aldehyde to the pro tein solution an insoluble methylene compound el iininated and the protein content rendered insoluble, if the aldehydes or compounds splitting ofi aldehydes are mixed with the protein solution, preferably prior to its incorporation in the cellulosic spinning solution. The quantity of aldehyde necessary may be determined by any suitable method, for example by the Sorensen titration method, but the amount employed must be such that the free amino groups-of the protein is precipitated in the yarn upon extrusion of the spinning solution into an acid precipitating 'bath,

so that hardening of the yarn after it has been spun is no longer required? The amount of protein to be added to the cellu' lo'sic spinning solution is dependent upon the effect desired. For example; for ordinary pur poses in manufacturing a viscoseyarn'ha'ving an affinity for acid wool dyes, wherein the proteinous material consists of milk casein, from 20% to 25% of'cas'ein calculated on the cellulose content of the viscose. solution should be employed. l Spinning may be effected ln'any precipitating bath suitable for spinning viscose rayon. The addition of tanning agents to the precipitating bath or special treating baths may be-desirable toprevent stickiness of the spun yarn. Shou1d discolorationof the protein'ous material occur duringitspa'rtial decomposition a reducing agent maybe employed. For example, if an alkaline agent'is used the reducing agent may be a s'ulfite, hyposulfiteonthe like; whereas, if, decomposition is effected in an acid medium, stannous scribed in. Example 1.

so-formed thread is washed acid-free, dried and then desulfurized with NazS.

A determination of the nitrogen cbntent of the spun thread indicates that the thread contains 86% of the protein which was added to the viscose solution.

The finished yarn, when viewed under the microscope, exhibits a homogeneous structure throughout, -and when dye.d .with Neolanviolet 13, (Cibaijdyes in the samedye bath ratio and with substantially the same intensityas natural wool.

Example II "5 kilograms of normal viscose are mixed with analkalineproteinsolution obtained by the de- C'onipositionofBO grams of soy bean protein with an excesso'f NaOH, in the same manner as de- The spinning solution so-forined isspun in a precipitating bath consisting of 70% H20, Na2SO4, 10% MgSO4, 8% H2804 and 2% of the condensation product of cresyl sulfonic acid andformaldehyd eat a chloride or-ititanousjchloride may be employed.

Activated 'carbonfmay' likewise be employed to prevent discoloration of the solution.

' The.methodfby which ahomogeneous spinning solutionjis obtained has already, been, described, QandQyai-nspun from such a solution is of homo- 'fgeneous composition. V'Howe'v'er, I have found that the spun yarn may be greatly improved and it .t'ensile stren gth increased considerably ii the "yarn, after spinhingyis passed through asecond bath containingsalts and a small amount of acid, and is subjected therein to a stretch in the neighborhood of 65%.

. The following examples will'serve toillustrate" methods for'conductingthe present invention.

Example .I l80.'grams of casein are dissolved in 800 grams of water and '72 grams .NaOH. To this solution 20 gramsNaOH and 5 grams of NazSO; are added and the mixture heatedat .95 C. until a drop of the solution can be homogeneously mixed with several .drops of normal viscose solution. The ,Qen'tire, reaction should require about 25" minutes and thehomog'eneityof the solution may be easily determined under themicroscope. The alkaline protein solution is thereupon cooledand'flltered.

The protein solution isnow treated with formaldehyde, the amount required in order to saturate the free amino groups of the protein, as

determined, for example, by the Sorensen titra tion' method, being in the ratio of 26 grams of commercial formalin to each kilogram of protein solution." m

500 grams of the protein-formalin solution are now mixed with 5 kilograms of normal viscose,-

containing about 8% cellulose. The mixture is then spun in a precipitating bath which contains 5% MgSOr, 15% NazSO4 and 8% H2804, and the 75 i the appended claims.

100 grams, of casein are l boiled with 1 liter of 15%..sulfuric acid and.,,10 c. of a solution of tit'anousv chloride in HCl, for two hour sin I a reflux condenser. and the resulting solutionl'decolorized with a little activatedfcarbon. The solution isdiluted with an equal volume of water and then neutralized with 30%. lye until it reacts light red. to methyl red, a thick precipitate resulting.

. This precipitate isfilte'redjofhilwashed an'didi solved in400 grams'of 2% NaOI-IQfAftertIie addition of 15 grams of commercial formalinl the solution is mixed with 5 liters of a normalviscose and further treated as indicatedrin Example II.

, The spinning solution ,is; homogeneous throughout. Y

Having now described the invention, 2 it to be understood that-the method is notto be construed as limited to the particular materials-or procedures specified inthe foregoing specification, as it is to be limited only 'byithe scope'of What is claimed is: e e

p l. A method of manufacturing'viscose threads of fwool like" character which comprises" dispersing casein in an; alkaliriei solution and heating the dispersiontohydrolyze the casein to an extent sufficient to be homogeneously-mixed with a viscose solution, saturatingtheiree amino groups of the casein with formaldehyde, mixing the' casein-formaldehyde solution with a viscose solution, spinning the mixturethrough'an acid precipitating bath'to form threads therefrom and completing the regeneration of the' threads in a secondbath maintained at a" temperature of about C. while stretching the same, whereby substantially the entire casein content is retained in the thread and may be dyed with acid wool dyes.

2. A method of producing a homogeneous viscose-protein spinning solution comprising partially hydrolyzing a protein of the class consisting of casein, soy-bean protein and zein, said hydrolysis being suificient to cause the protein to mix homogeneously with a viscose solution determinable under the microscope andsufilcient to cause the solution to coagulate immediately with a dilute acid, and mixing the partially hydrolyzed protein with a viscose solution.

3. A method of producing a homogeneous viscose-protein spinning solution comprising parto cause the solution to coagulate immediately with a dilute acid adding an aldehyde to the partially hydrolyzed protein to harden the same and finally mixing the protein-aldehyde solution with a viscose solution.

THEODOOR KOCH. 

